1. Field
The present invention relates to a hermetic compressor, and, more particularly, to a hermetic compressor, which can attenuate a discharge pulsation caused upon discharge of a refrigerant, thereby reducing a vibration and noise.
2. Description of the Related Art
Generally, a refrigeration cycle employed in a refrigerator, etc. performs compression, condensation, expansion, and evaporation processes in sequence using a refrigerant as a medium. As one of the devices to perform the compression process, a reciprocating type compressor is configured such that a piston slidably reciprocates in a compression chamber to discharge a high-temperature/high-pressure refrigerant. The reciprocating type compressor includes a hermetic container defining the outer appearance of the compressor, a drive device received in the hermetic container to generate power, and a compression device to suction and compress a refrigerant upon receiving the power from the drive device so as to discharge a high-temperature/high-pressure refrigerant. The reciprocating type compressor is also referred to as a hermetic compressor.
More specifically, the compression device is located in a lower region of the hermetic container. The compression device includes a cylinder block to define the compression chamber, a piston to reciprocate in the compression chamber upon receiving the power from the drive device, and a cylinder head provided at a tip end of the cylinder block, the cylinder head having a refrigerant suction chamber and a refrigerant discharge chamber defined therein.
A valve assembly is provided between the cylinder block and the cylinder head. The valve assembly has a suction hole and a discharge hole to communicate the suction chamber and the discharge chamber with the compression chamber. The suction hole and the discharge hole are provided with a suction valve and a discharge valve, respectively, to adjust the flow of a refrigerant.
A suction muffler is disposed at the top of the cylinder head to attenuate a noise caused upon introduction of a refrigerant. The suction muffler is connected with a refrigerant inlet pipe. In addition, a discharge muffler is mounted at a lower surface of the cylinder block to attenuate a pressure pulsation caused upon discharge of a high-temperature/high-pressure refrigerant. The discharge muffler is connected with a refrigerant outlet pipe. In this case, to communicate the discharge muffler with the discharge chamber of the cylinder head, a communication path is defined in the cylinder block.
In the operation of the hermetic compressor having the above described configuration, if the piston moves to a bottom dead center of the compression chamber, a refrigerant is introduced into the compression chamber through the suction muffler and the suction chamber. Thereafter, as the piston moves to a top dead center of the compression chamber, the refrigerant is compressed and discharged into the discharge chamber of the cylinder head. Subsequently, the refrigerant is discharged into the discharge muffler through the communication path of the cylinder block.
However, since the above described reciprocating type compressor suctions, compresses, and discharges a refrigerant as the piston rectilinearly reciprocates in the compression chamber, it cannot continuously discharge the refrigerant and causes a discharge pulsation. The discharge pulsation of the refrigerant results in a vibration and noise of the compressor. In particular, a compressor noise generated in a low-frequency band of the discharge pulsation corresponding to a natural frequency of other elements of a refrigerator has a resonance with the elements, increasing a vibration and noise of the refrigerator.
To attenuate a noise generated from the discharge chamber of the cylinder head, it is necessary to consider certain factors, for example, the volume of the discharge muffler, and the length and cross-sectional area of a tube to communicate the discharge chamber with the discharge muffler, which has an effect on the natural frequency of the discharge muffler.
Although it has been proposed in the prior art to attenuate a discharge pulsation by increasing the volume of the discharge muffler, a limited inner space of the compressor makes it impossible to increase the volume of the discharge muffler beyond a predetermined level. Further, since the communication path is defined in the cylinder block, the length of the communication path is limited by the size of the cylinder block. Accordingly, it is difficult to prevent a discharge pulsation and low-frequency noise, and in particular, the low-frequency noise makes a person uncomfortable.